ack in 1975, “Jaws” made us all afraid to go back into the ocean – the movie was scary enough to make you swear off swimming altogether. Steven Spielberg’s movie was rousing and just about perfectly executed, made even more so, ironically enough, as a result of the director’s resourcefulness when faced with the technological imperfections of his star villain. For similar reasons, I also loved the original “Piranha.” Director Joe Dante, working from the Roger Corman manual for turning budgetary and technical limitations into virtues rather than hindrances, made the “Jaws” knock-off of all “Jaws” knock-offs. But he also gave interior-dwelling landlubber movie fans a terror-in-the-water movie all our own. Now us rural hicks could wonder about the wisdom of dangling our feet off the pier of a picturesque lake or reservoir, imagining the flesh on our toes and ankles and thighs being shorn free of flesh by ravenous piranha set loose in the fresh water by an all-too-typical military-industrial snafu. And now, whether we needed one or not, “Piranha 3D” invites us back in for another swim.

Director Alexandre Aja (“High Tension,” “The Hills Have Eyes”), armed with a bigger budget than Corman ever doled out (though considerably less than the usual 21st century blockbuster) has rigged – in terms of sheer body count, anyway – the biggest fish food feast yet. “Piranha 3D” is a swiftly-paced strain of B-movie exploitation that craftily employs 3D in service of an orgiastic explosion of nubile, oiled-up boob jobs and drunken behavior doubling as a very bloody dinner for a nasty school of meat-eating fish. The hungry schools are set loose on a bustling resort town (Lake Havasu standing in for fictional Lake Victoria) when an earthquake opens a fissure under the lake that connects it to a prehistoric piranha breeding ground. And the movie doesn’t waste much time plating these gill-laden Tasmanian Devils their first meal – a grizzled old fisherman named Matt, played by Richard Dreyfuss, who quickly gets stripped to the bone and whets the beasties’ appetite for more gristle and gore.

Lake Victoria Sheriff Julie Forrester (Elisabeth Shue) and her deputy (Ving Rhames) already have their hands full when their vacation location is invaded by thousands of hard-partying college punks on spring break. But when a team of visiting seismologists (headed by Adam Scott) dive down to investigate the damage done by the quake at lake bottom, they discover (in the most inconvenient fashion possible) the true gravity of the situation and just how hungry those little swimmers really are. Meanwhile, Forrester’s fresh-scrubbed son Jake (Steven R. McQueen) is recruited by a “Girls Gone Wild”-type softcore porn king (Jerry O’Connell) to scout locations for his latest production, with Jake’s only-slightly-less-fresh-scrubbed girlfriend (Jessica Szohr), a foxy but good-hearted model (Kelly Brock), and a goofball cameraman (Paul Scheer) all along for the ride. To complicate matters, Jake is supposed to be babysitting his younger brother and sister who (no surprise) instead find their way on board O’Connell’s luxury boat, at which point the dinner bell commences to ringin’.

Aja and his screenwriters, Peter Goldfinger and Josh Stollberg, take perhaps a bit too much time setting up the main course, but ultimately the wait pays off. They prove astute at imagining all the different ways 3D can be employed to hurl various items at the audience, some more appreciated that others. There’s enough bikini-busting, silicone-enhanced breasts comin’ at ya in “Piranha 3D” that each ticket purchased ought to come with an application to the nearest zeppelin traffic controller school, and a surprise comic puking scene finds the audience with just the right perspective to encourage lap-checking for fallout afterward. Aja also stages a hilarious underwater girl-on-girl ballet/make-out session scored to Delibes’s “Flower Duet” – all being filmed for O’Connell’s video opus, of course – that is as hilarious and brashly up front about its intentions as anything Russ Meyer ever put on film. (A certain percentage of ticket-buyers for “Piranha 3D,” waiting patiently for the gore, will find their annoyance at having to wear those 3D glasses assuaged completely by this scene.)

Once the carnage does get into high gear, I began to really appreciate the efforts of the filmmakers to paint almost everyone beforehand with such broad a-hole strokes. It’s a move that serves to accentuate the fun as those razor-sharp teeth start turning the churning water a nice shade of crimson. Who wouldn’t want to see these nincompoops get chummed? Aja’s visual instincts as to what exactly to chuck at the audience once the swimmers start getting separated from their arms and legs (and other appendages) remain spot on as well, and I wouldn’t dream of spoiling the fun by going into much more detail than that. The humorous karma delivered on these boneheads keeps the escalating water-bound slaughter from crossing the line into simple barbarism – the producers of the endless “Saw” sequels and their heartlessly gory progeny could learn a little bit about how to mix humor with horror from this movie. (Only one sequence, in which a long-haired beauty gets her tresses tangled up with a boat propeller while her lower extremities are being gnawed away, flirts with real ghastliness.) At the peak of the action, a large expanse of Lake Victoria having been turned the hue of a hearty burgundy, victims flailing and screaming and scrambling to no avail, my friend turned to me and cracked, “It’s like ‘Gone with the Wind’!” Indeed, “Piranha 3D”’s climactic aqua-picnic is so epic in scale, so eager to spill blood and render skin asunder from skull in the name of entertainment, that it plays like the Fangoria fan’s equivalent of the burning of Atlanta.

There is the matter of the movie’s 3D being of the post-production conversion variety, which means that the picture is old-school muddier than the grade-A digital variety we’ve become used to from movies originally shot in the depth-producing process. That muddiness isn’t so much a problem above the surface, but the underwater depths are dimmer than they need to be, even when the fish are flying straight for your face. Mind you, this is not the 2010 equivalent of “Jaws 3D” – no movie could get away with being that murky in these times of “event pricing.” But when the action accelerates and Aja leans too heavily on the editing to convey a sense of panic beneath the waves, “Piranha 3D” loses some of the edge, some of the balls-out comic frenzy the filmmakers have brought to the project overall.

Even so, the slightly dirty exhilaration to be had from a good, clean genre exploitation movie is easier to pitch than to actually pull off, and “Piranha 3D” gets honestly earned points for the creative energy it sustains in the arena of creatively gory dispatches, non-torture porn division. (The outstanding effects are courtesy of maestros Howard Berger and Greg Nicotero.) It has a roster of fine lead players – Shue, Dreyfuss and O’Connell are particularly good sports – and knows exactly how to prime us to clamor for big and bloody terror when that cast-of-thousands-of-idiots spring break party finally gets crashed by prehistoric piranha. “Piranha 3D” is much more fun than all those other recent ‘80s horror retreads put together, even the relatively okay “My Bloody Valentine 3D,” and it deserves a healthy after-theatrical life. While waiting for the curtain to rise on this spectacle of hundreds of Young, Beautiful and Dumb People being eaten by a pack of fresh-water predators, my friend and I saw a preview for another movie with which, in a perfect world, “Piranha 3D” would seem destined to coexist. If some enterprising drive-in or repertory house ever has the audacity to pair this terrific, unapologetic B-movie with “Jackass 3D” it could be the Darwin Awards double feature of all time.

Single-Disc DVD Review:

Sony’s DVD release of “Piranha 3D” (now simply being called “Piranha” due to the fact that it’s only available in the 3D format on Blu-ray) may not look like much, but the included bonus material is definitely a matter of quality over quantity. Though the audio commentary by writer/director Alexandre Aja and producers Gregory Levasseur and Alix Taylor isn’t necessarily a must-listen, the five-part featurette, “Don’t Scream, Just Swim,” more than makes up for it with a behind-the-scenes look at making the film.